Phonographic apparatus



1941- J. J. HGEHN 2,260,319

PHONOGRAPHIC APPARATUS 2 Sheets-Sheet 1 Filed Nov. 30, 1939 Oct. 28,1941. J J HOEHN 2,260,319

PHONOGRAPHIC APPARATUS 2 Sheets-$heet 2 Filed Nov. 50, 1939 PatentedOct. 28, 1941 2,260,319 PHONOGRAPHIC APPARATUS John J. Hoehn,

Indianapolis, Ind., assignor to Radio Corporation of America, acorporation of Delaware Application November 30, 1939, Serial No.306,832

8 Claims.

This invention relates to phonographic apparatus, and more particularlyto the turntable driving mechanism thereof, the present invention beingan improvement over that disclosed and claimed in the oopendingapplication of Raymond F. Brady and Paul Weathers, Serial No. 260,282,filed March '7, 1939, and assigned to Radio Corporation of America.

In the aforesaid application, there is disclosed a turntable drivingmechanism comprising a motor having a drive shaft formed with a steppedpulley between which and the turntable rim a floating idler wheel may beinterposed to transmit torque from the motor shaft to the turntable atone or another of two speeds, as may be desired, the drive mechanismconstituting a part of phonographic apparatus which may be used both forrecording sound on a blank disc and then playing the recorded disc back.While this drive mechanism is very satisfactory for the transmission oftorque to the turnable, one of the weaknesses inherent in a system ofthis kind is that the speed of the turntable is reduced in directproportion to the friction or load which is applied to the turntable.This loss in speed is not due to the frictional losses or slippagebetween the idler wheel and the turntable but is caused partly by thedisplacement or stretching of the rubber of the rubber-tired idler atthe periphery of the idler pulley.where it engages the motor shaft.Since the drag on the turntable exerted by the reproducing stylus of apickup device is much smaller than that exerted by the recording orcutting stylus in recording sound upon a disc, the displacement of therubber on the idler pulley is greater during the recording process thatit is when the record is being reproduced.

The primary object of my present invention is to provide an improveddriving mechanism for the turntable of the type set forth above by meansof which the foregoing difllculties will be obviated.

More particularly, it is an object of my present invention to provide animproved turntable drivnism of the type set forth wherein the pressureloading against the motor pulley or shaft is approximately sided bearingloading in the motor which is inherent in the driving mechanismdisclosed in the lng speeds, and which is relatively inexpensive ingmechanism as aforesaid by means of which the speed differential betweenthe recording and reproducing speeds of the turntable is minimized.Another object of my present invention is to provide an improvedturntable drive mechanism of the type set forth above which is smooth inoperation and which operates at great efllciency both during recordingand reproduction.

A further object of my present invention is to provide an improvedturntable driving mechain cost.

In accordance with my present invention, I provide a second idler pulleyor friction wheel between the driving motor shaft and the turntable andmount this friction wheel on a separate lever arm symmetrically oppositeto the conventional single idler pulley relative to the motor drivingshaft. The transmitted load is thus divided between the two idlerpulleys. Separate tension springs may be employedone ion each idler orfriction wheel, to hold the two friction wheels in engagement with thesingle motor shaft and the turntable. A single control lever which iscommon to both of ing arms is arranged to effect a camming action uponsaid arms to move them away from torque transmitting position. Thiscontrol lever may also be made to operate a switch in circuit with thedriving motor. When the arms which support the friction wheels are inseparated relation, that is, in open" position, these levers, togetherwith their friction wheels, may be shifted longitudinally along themotor shaft by means of an adjusting knob to bring the friction wheelsopposite preselected portions of the driving motor to the respectivespeeds at.

shaft corresponding which it is desired to operate the turntable.

The novel features that I consider characteristic of my invention areset forth with particularity in the appended claims. The inventionitself, however, both as method of operation, together with additionalobjects and advantages thereof, will best be Iiderstood from thefollowing description of several embodiments thereof, when read inconnection with the accompanying drawings, in which Figure 1 is a planview of one form of my invention adjusted for operation at a relativelyslow speed, for example, 33 R. P. M.

balanced, thereby reducing the one-- the friction idler support to itsorganization and Figure 2 is a similar fragmentary view (certain of theDarts being omitted for the sake of clearness) showing the couplingidlers in the position to drive the turntable at a relatively highspeed, for example, 78 R. P. M.

Figure 3 is a side elevation of this form of my invention with the partscorresponding to the position shown in Figure 1, and

Figures 4, and 6 are, respectively, views similar to Figures 1, 2 and 3but showing a somewhat different form of my invention.

Referring more particularly to the drawings, wherein similar referencecharacters represent corresponding parts throughout, there is shown amotorboard I to which is secured a motor plate 3 carrying a motor 5. Themotor plate 3 is provided with an opening through which extends themotor shaft 1, the latter being formed with a relatively small diameterdriving portion Ia at its upper extremity and a relatively largediameter driving portion Ib immediately below the portion la. Above themotorboard I is mounted in conventional manner a turntable 3 having anannular rim or flange 9a.

Fixed to the motor plate 3 is a post II (see Fig. 3) on which arepivotally carried a pair of supporting levers or arms I3, one of thearms being formed with a bend I3a therein so that the free ends of thearms I3 are both on the same level, as clearly shown in Fig. 3. Atubular member I5,which is rotatably and slidably mounted on the postII, rests on a collar I4 to which the two levers I3 are connected, and acoil spring I1 which surrounds the post I I levers I3 and the tubularmember I5 to an elevated position. A pin I 9 secured to the post I Icooperates with a bayonet slot 2| in the tubular member I5 to limit themovement of the member I5 on the post II.

Pivotally mounted on each of the levers I3 is another lever 23 on thefree end of which is rotatabiy mounted a rubber-tired friction wheel oridler 25 which acts as a coupling idler between the shaft 1 of the motorand the turntable flange 9a. Each of the levers I3 has a pin 21 thereonwhich fits up into an opening 29 in the to limit the movement of thelevers 23 with respect to the levers I3. A pair of tension springs 3I,each having one end secured 33, which is fixed on the motor plate 3, andhaving their other ends secured to the lower ends of the downwardlyextending pins 21 on the lever arms I3, serve to constantly urge thesupporting arms I3 into a position such that the friction wheels 25 willengage the motor shaft 1 and the turntable flange 9a. Since the levers23 are free to float on the supporting arms I3 within the limitsdetermined by the pins 2'! and the openings 29, the friction wheels 25will both be able to center themselves between the turntable peripheryand the motor shaft. The parts are so arranged that, when the frictionwheels 25 are in torque transmitting position, that is, in engagementwith both the motor driving shaft 1 and the turntable periphery 9a, asclearly shown in Figs. 1 and 2, the friction wheels are symmetricallydisposed on opposite sides of the motor shaft I with respect to a linejoining the axes of the motor pulley I and the post II.

Each of the supporting levers I3 is provided with a lateral extensionI3b formed with a. cam edge I6 and a side edge I8, the edges I8 being insubstantially parallel relation when the lever arms I3 are in thepositions shown in Figs. 1 and 2. A control lever 37 having an upwardlyexengagement with the motor shaft 1 and the turntable flange 9a.

To drive the turntable at 33 R. P. M., the cylindrical sleeve I5 ispermitted to remain in its most elevated position, as shown in Fig. 3,with the pin I 9 engaging the lowermost extremity of the slot 2|. Allthis time, of course, must be in its most counter-clockwise position sothat the friction wheels 25 will be clear of the motor shaft I. With thesleeve I5 in its most elevated position, the spring I 1 will hold thesupother of its extreme positions, as above described.

When it is desired to drive the turntable 3 at '78 R. P. M., the controllever 31 is again moved counter-clockwise on its pivot post I until theover-center spring 44 holds the lever 31 in its extremecounter-clockwise position, at which time the pin 43 will have beenwedged in between the edges I8 to separate the arms I3, and thus holdthe friction idlers 25 out of engagement with the motor shaft I and theturntable flange 9a and clear of even the largest diameter of the motorshaft I. At such time, the cylindrical sleeve I5 may be presseddownwardly as far down as it will go against the action of the spring I!and then turned slightly clockwise, as viewed in Figs. 1 and 2, so thatthe portion 2Ia of the bayonet slot 2| will be brought into engagementwith the pin I9. This brings the friction wheels 23 down to the level ofthe large diameter portion lb of the motor shaft, and when the controllever 31 is next returned tothe position shown in Fig. 2, the couplingidlers 25 will be brought into engagement with the driving shaft portion117 and with the turntable periphery fluence of the coil springs 3|.

The circuit to the motor 5 is preferably controlled by means of a toggleswitch 43 which has 9a under the ina forked operating lever 48. A pin llon the control lever 31 extends down through an openin: in the motorplate 3 and is received by the forked lever 48. Thus, when the controllever 31 is moved'to its extreme counter-clockwise position, the switchlever 49 is caused to move to a position to open the switch-48 andthereby break the motor circuit, whereupon the motor shaft 1 ceasesrotation. However, when the control lever 3 is moved to its extremeclockwise position, it will automatically move the switch lever 49 to aposition to close the circuit of the motor 5 and thereby once moreautomatically effect rotation of the motor shaft 1.

In the modification of my invention shown in Figs. 4, 5 and 6, I haveshown a construction similar to that described above. Ir. thismodification, however, the supporting arms i3 are formed with extensionsi3 which combine to provide a fork. A bushing 53 on the motor plate 3rotatably receives a control member 55 which is provided with anoperating" handle 51 and is formed with acam 58 received between thefork formed by the supporting arm extensions l3.

Each of the arms i3 has a pin SI thereon to which one end of a separatetension spring 53 is secured in each case, the other ends of the springs63 being respectively secured to brackets 55 slidably mounted on themotor plate 3 for adjustment thereon, so that the tension in the springs63 maybe varied. The springs 63 constantly tend to turn the supportingarms i3 in directions such that the friction idlers 25 will be biasedinto engagement with the motor shaft 1 and the flange 9a of theturntable. The cam portion 59 of the control member 55 is narrower, intransverse section, than the distance between the arm extensions II whenthe idlers are in torque transmitting position, as clearly shown inFigs. 4 and 5. However, when it is desired to disconnect the frictionwheels 25 from the motor shaft 1 and the turntable flange 9a, thecontrol member 55 may be turned in its bushing 53 in a counterclockwisedirection whereupon the cam 59, which has a length in cross-sectiongreater than the distance between the arm extensions II, will force thearm extensions l3 apart against the action of the springs 63 and therebyremove the friction idlers 25 from driving engagement with the motorshaft and the turntable. At the same time, a cam plate 61 on a collar 69which is secured to the lower end of the control member 55, as by meansof a set screw H, serves to operate the toggle arm 13 of a motor switch15 in circuit with the driving motor 5. For this purpose, the cam plate61 is formed with two high portions B'Ia and 61b, the portion 61bengaging the toggle arm 13 when the control member is turned to its mostcounter-clockwise position to turn the switch to off position, and theportion 61a engaging the toggle arm 13 to turn the switch back to onposition when the control member 55 is moved back to its most clockwiseposition, as shown in Figs. 4, 5 and 6. In other respects, themodification of the invention shown in Figs. 4 to 6 is similar to thatshown in Figs. 1 to 3.

From the foregoing description, it will be ap parent to those skilled inthe art that I have provided an improved turntable driving mechanismwhich will drive the turntable at a very uniform and accurate speed bothduring recording and reproduction, and that the variation between therecording and reproducing speeds will be a minimum. The use of a singlemotor with a plurality of coupling idlers has the advantage of insuringmore uniform speed, since each of the idlers is driven by the samemotor. Moreover, with a construction such as described loading againstthe motor shaft is fairly balanced and bearing loading on the motorshaft inherent in driving mechanisms employing a single friction wheelis practically eliminated. This greatly improves the bearing rumblecondition. Another advantage of my improved driving mechanism is thatthe load on each rubber tire of the friction wheels 25 is reduced whentwo idlers are used, and this results in increased tire life.

Although I have shown and described but two embodiments of my invention,it will be apparent to those skilled in the art that many othermodifications, as well as changes in those described, are possible. Itherefore desire that my invention shall not be limited except insofaras is made necessary by the prior art and by the spirit of the appendedclaims.

I claim as my invention:

1. In phonographic apparatus, the combination of a motor having adriving shaft, a turntable, a pair of supporting members, a frictionwheel carried by each of said supporting members, said friction wheelsbeing floatingly mounted with respect to their respective supportingmembers, said supporting members being mounted for movement from and toa position such that said friction wheels will engage the periphery ofsaid turntable and said shaft to provide a plurality of drivingcouplings therebetween, and control means common to both of saidsupporting members for simultaneously controlling the movement of saidmembers into and out of said position.

2. In phonographic apparatus, the combination of a motor having adriving shaft formed with portions of different diameters, a pair ofsupporting members, a friction wheel carried by each of said supportingmembers, said supporting members being movably mounted for adjustmentalong the length of said shaft, means for adjusting said members alongsaid shaft to bring said friction wheels into alignment with anypreselected one of said shaft portions and said turntable periphery,said members being also mounted for movement from and to a position suchthat said friction wheels will engage the periphery of said turntableand the preselected portion of said shaft to provide a plurality ofdriving couplings between said shaft and said turntable, and controlmeans common to both of said supporting members for simultaneouslycontrolling the movement of said members into and out of said position.

3. In phonographic apparatus, the combination of a motor having adriving shaft, a turntable, a pair of supporting arms mounted forpivotal movement relative to said shaft, a friction wheel carried byeach of said arms, said friction wheels being floatingly mounted withrespect to their respective supporting arms, said arms being movabletoward said shaft to bring each of said friction wheels into engagementwith said shaft and said turntable to provide a plurality oftorquetransmitting couplings therebetween and being movable away fromsaid shaft to break said couplings, and means common to both of saidarms for controlling the movement of said arms into and out of saidtorque-transmitting position.

4. In phonographic apparatus, the combination of a motor having adriving shaft, a turntable, a pair of supporting arms mounted on acommon axis for pivotal movement relative to said shaft, a frictionwheel carried by each of said arms, said above, the pressure frictionwheels being noatingly mounted with reto constantly urge said arms intotorque-tramspeot to their respective supporting arms. said mittingposition, and characterized further in arms being movable on said axistoward said that said control means includes means for camshaft to bringeach of said friction wheels into ming said arms away from said shaftsimultaneengagement with said shaft and said turntable to ously to breaksaid coupling. provide a plurality of torque-transmitting cou- 8. Inphonographic apparatus, the combination plings therebetween and beingmovable away of a motor having a driving shaft provided with from saidshaft to break said couplings, and portions of different diameters, aturntable, a means common to both of said arms for conplurality offriction wheels adapted to transfer trolling the simultaneous movementof said arms 10 torque from said shaft to said turntable, said into andout of torque-transmitting position. friction wheels being mounted formovement into 5. The invention set forth in claim 4 characengagementwith the periphery of said turntable terized by the addition of meansconstantly urgand any one of said shaft portions at will wheren Sa d a snto torq es n position. by to drive said turntable at any preselectedone 6. The invention set forth in claim 4 character- 15 of a pluralityof speeds,- and means common to ized in that said control means includesmeans 5110f 1 friction wheels for simultaneously for moving said armsaway from said shaft trolling the movement thereof into and out ofwhereby to break said coupling. torque-transmitting position at will.

'7. The invention set forth in claim 4 characterlzed by the addition ofspring means arranged 20 JOHN J. HOEHN.

